VI.—The Relation of the Red to the Norwich Crag

Abstract

Perhaps no question in English Pliocene geology has caused so much inquiry as the exact relation of the Red and Norwich Crags. The latter term I prefer as more palæontologically correct than the older one of “Mammaliferous,” and it is now becoming generally used. In the year 1865 I divided the Norwich Crag into two divisions, an Upper and a Lower, and endeavoured to show that the latter was the true Fluvio-marine Crag, the former being distinguished by its purely marine character, and also by its containing a larger per-centage of Northern shells. This Upper Crag was subsequently termed the “Chillesford Crag” by Mr. Searles Wood, and by this name it is usually known. In my paper above mentioned my purpose was to show that this Upper or “Chillesford Crag” connected the latest of the older crags with the lower Drift-beds. The Fluvio-marine beds were formed along the floor of an estuary, but the Upper Crag was deposited along the sea-bottom, when the same area had been depressed. As a consequence, this Crag had a wider and more extensive geographical development. I was unaware at this time that Mr. Searles Wood was working at the same subject; and I subsequently found that he, with his usual indefatigability, had arrived at a similar conclusion respecting the Upper bed of Norwich Crag.